Rhizomania is the most destructive disease in sugar beet throughout the world. The disease is caused by Beet necrotic yellow vein virus (BNYVV). Polymyxa betae (Keskin) is the only known vector of BNYVV, for transmission of the virus between the plants. Developing molecular diagnostic methods has a major impact on forecasting and epidemiological studies as well as screening sugar beet plants used in resistance breeding programmes. In the present study, quantum dots (QDs) were biofunctionalized with a specific antibody against P. betae. The glutathione-S-transferase protein's (GST) corresponding antibody (anti-GST) was effectively conjugated to Tioglicolicacid-modified Cadmium-Telluride QDs (CdTe-QDs) synthesized in an aqueous solution via electrostatic interaction. The dye (Rhodamine) molecules were attached to the GST. Donor–acceptor complexes (QDs-Ab-GST-Rhodamine) were then formed based on the antigen–antibody interaction. The mutual affinity of the antigen and the antibody brought the CdTeQDs and rhodamine together close enough to allow the resonance dipole–dipole coupling required for fluorescence resonance energy transfer (FRET) to occur. The immunosensor constructed showed a high sensitivity and specificity of 100%, acceptable stability and could be used for real sample detection with consistent results. To the best of our knowledge, this is the first report on designing a nano-based biosensing tool for the detection of plant pathogenic fungi.

The fabrication of the first label-free electrochemical DNA probe biosensor for highly sensitive detection of Candidatus Liberibacter asiaticus (CLas), as the causal agent of citrus huanglongbing disease, is conducted here. An OMP probe was designed based on the hybridization with its target-specific sequence in the outer membrane protein (OMP) gene of CLas. The characterization of the steps of biosensor fabrication and hybridization process between the immobilized OMP-DNA probe and the target ssDNA oligonucleotides (OMP-complementary and three mismatches OMP or OMP-mutation) was monitored using cyclic voltammetry and electrochemical impedance spectroscopy based on increasing or decreasing in the electron transfer in [Fe (CN)₆]^3−/4− on the modified gold electrode surface. The biosensor sensitivity indicated that the peak currents were linear over ranges from 20 to 100 nM for OMP-complementary with the detection limit of 0.026 nM (S/N = 3). The absence of any cross-interference with other biological DNA sequences confirmed a high selectivity of fabricated biosensor. Likewise, it showed good specificity in discriminating the mutation oligonucleotides from complementary target DNAs. The functional performance of optimized biosensor was achieved via the hybridization of OMP-DNA probe with extracted DNA from citrus plant infected with CLas. Therefore, fabricated biosensor indicates promise for sensitivity and early detection of citrus huanglongbing disease.

Tomato brown rugose fruit virus (ToBRFV) is a single-stranded positive-sense RNA virus that targets tomato and pepper plants and is causing significant damage to crops in some regions of the world. ToBRFV is a highly contagious virus that is stable and rapidly spreads by mechanical methods and seeds. As a result, it may spread both locally and over long distances, and it is now recognized as a pandemic in plants. This study investigates the effectiveness of the systems CRISPR-Cas12a and CRISPR-Cas9, in conjugation with recombinase polymerase amplification (RPA), to detect ToBRFV in tomato plant samples collected from the field. The trans-cleavage activity of both nucleases, Cas12a and Cas9, was exploited to process a probe labelled with fluorescein and biotin to be resolved on a lateral flow device, thereby enabling a visual readout. We were able to detect the RNA genome of the virus in about 1 h at a low constant temperature. These results could pave way to offer a rapid, sensitive, and specific method for on-site detection of ToBRFV.